Influence of humans and domestic animals on the household prevalence of Trypanosoma cruzi in Triatoma infestans populations in northwest Argentina.

Abstract

Abstract. In three rural villages of northwest Argentina, the overall proportion of domiciliary Triatoma infestans infected with Trypanosoma cruzi was 49% among 1,316 bugs individually examined for infection in March and October 1992). Most of the variation among individual households in the proportion of infected triatomines was explained by variations among houses in the proportion of bugs that fed on dogs or cats, the prevalence of infected dogs or cats, and the proportion of bugs that fed on humans, according to a logistic multiple regression analysis. The effects of human infection rates on bug infection rates were not statistically significant. After adjusting for the effects of other predictors, the presence of chickens in bedroom areas had negative and significant effects on the proportion of infected Triatoma infestans, and positive and significant effects on the number of T. cruzi-infected triatomines collected per person-hr per house. Dog or cat infection rates and the proportion of bugs that fed on dogs or cats and on chickens explained 80% of the total variance of infected-bug numbers in a linear multiple regression model. This is the first study to use detailed field data to show that variations in triatomine infection rates depend on bug host feeding patterns and dog or cat infection rates, while the presence of chickens in bedroom areas exerts opposite effects on the proportion and number of infected triatomines. Domestic animals play a crucial role in the domiciliary transmission of T. cruzi.Triatoma infestans Klug, probably the most important and widespread domiciliary vector of Trypanosoma cruzi, 1 showed one of the highest rates of infection with T. cruzi (median ϭ 34%, range ϭ 12-68%) in extensive surveys carried out when insecticidal campaigns were nil or at an early stage in several countries. 2 For young men drafted into military service from all over Argentina, the Province of Santiago del Estero (northwest Argentina) had the highest prevalence rate of seropositivity for T. cruzi among all provincewide prevalence rates in the period 1964-1969 when the first screening took place, and the third highest prevalence rate in 1981. 3 In this province, the percentage of T. cruzi-infected Triatoma infestans collected from human sleeping quarters (hereafter domiciliary areas) was high (44%) and widely variable (range ϭ 21-82%) from district to district. 4 More recently, domiciliary vector infection rates were 31% more than 10 years after the first spraying of houses with insecticides in northwest Santiago del Estero. 5 Explaining such variable infection rates of domiciliary triatomines within a given community or province may increase our understanding of the transmission dynamics of T. cruzi.Vector feeding patterns link hosts, vectors, and the transmission of parasites in either direction between hosts and vectors. Dogs, chickens, and humans are the most important host blood sources of domiciliary Triatoma infestans throughout its range. 6 In northwest Argentina, the feeding pattern of domiciliar...

Seroprevalencia de la infección por Trypanosoma cruzi y factores asociados en un área endémica de Venezuela

“…Sin embargo, en este trabajo no hubo correlación entre las casas con individuos seropositivos y las casas con perros seropositivos, por lo tanto, el perro actualmente no se está comportando como un reservorio, sino que estaría marcando una costumbre de las familias seropositivas en relación con la preferencia o necesidad de convivir con estos animales. Las gallinas son fuentes de alimento para los triatominos y su presencia en las aéreas domiciliarias impactan la ecología doméstica de la enfermedad de Chagas, ya que, incrementan la infestación del domicilio, conllevando a un incremento en el contacto del vector con los reservorios domésticos, aumentando de esta manera el número de triatominos infectados 35,36 . En este sentido ha sido sugerido que el éxito reproductivo de R. prolixus se ve favorecido con mayor fecundidad si en el domicilio ocurriera la ingesta con sangre humana, pero si previamente el insecto se ha alimentado sobre gallina 37 .…”

Autonomic Dysfunction and Risk Factors Associated with Trypanosoma cruzi Infection among Children in Arequipa, Peru

“…40 The risk factors that we identified for urban transmission of Chagas disease were quite similar to those found in rural epidemiological studies. 20,22,41 Not surprisingly, household members' reports of triatomine infestation as well as traces of triatomine exuvia or feces in the child's room were very strong predictors of infection. However, household infestation rates based on bugs collected by the Ministry of Health spray teams were not strongly associated with the child's risk of infection.…”

“…18,19 Although risk factors for T. cruzi infection have been studied in a number of rural settings, there are few data from urban foci of transmission. [20][21][22][23][24] Our group's investigations in periurban Arequipa showed increased risk of triatomine infestation associated with domestic animals, unplastered house walls, and animal pens, and showed the highest prevalence of human T. cruzi infection to be located on the densely populated hillsides outside the city. 25,26 In the present analysis, we examined risk factors for T. cruzi infection and compared EKG findings and four tests of parasympathetic autonomic function in infected children and matched uninfected control children.…”

Seroprevalencia de la infección por Trypanosoma cruzi en la población rural del estado Sucre, Venezuela

“…Se ha demostrado que la presencia de aves y perros en el domicilio está asociado a la seropositividad en humanos 32 . La presencia de aves (gallinas) en el domicilio constituye una fuente de alimento para los triatominos, en consecuencia aumenta la densidad poblacional de estos en las viviendas, un mayor contacto de los vectores con los reservorios domésticos, incrementando la probabilidad de triatominos infectados y por ende de humanos positivos 33,34 .…”

“…Los insectos triatominos pueden ser encontrados dentro de diferentes ecotopos, estos pueden dispersarse pasivamente de medios silvestres o selváticos a medios peridomésticos 33,34 . Algunas especies asociadas a la madera en el ambiente natural, frecuentemente son introducidas en medios ambientes artificiales a través de la leña 35 .…”